A growing number of police departments across the U.S. are adding prescription drug drop-off boxes at stations to allow people to properly dispose of expired or unneeded drugs.

Organizations like the National Association of Drug Diversion Investigators are providing grants to police departments to pay for the drop off boxes. Executive Director Charles Cichon said the organization began the program four years ago to address the lack of opportunities to safely dispose of prescriptions.

Pharmacies are not allowed to take back certain drugs, such as pain relievers and stimulants, because they are controlled substances. Take-back days hosted by the Drug Enforcement Administration are held occasionally in some cities and are often the only other way people can return substances properly.

In the last year, Pennsylvania has installed 250 boxes through a state program. In January, the state's Department of Drug and Alcohol Programs launched an interactive map showing all the statewide locations.

This month, four precincts in Staten Island, N.Y., also received drop off boxes.

Cmdr. Geoff Huff of the Ames, Iowa, police department said that improperly disposed of prescription drugs can be can be a major problem.

One common concern is people flushing old prescriptions down the toilet, which he called the "worst thing you can do." The drugs could eventually end up back in the water supply.

Drugs left in the home can end up in the wrong hands — children can accidentally ingest them or they may be stolen.

"We've seen an increase of our officers taking drugs off the street from people, and (the drugs) aren't theirs at all or they're being abused," Huff said.

Government officials have recognized a gap in the system. The DEA is working to change the rules governing secure disposal of controlled substances. Although the Controlled Substances Act of 1970 did not allow the ultimate users of prescription drugs to dispose of them, the Secure and Responsible Drug Disposal Act of 2010 gave the DEA an opportunity to change that.

The proposed rules, currently under review, would expand the options available for the collection of prescription drugs. These include more take-back events, programs to mail-back prescriptions and increased availability of collection receptacles, DEA spokeswoman Barbara Carreno said.

The National Association of Drug Diversion Investigator's Rx Drug Drop Box program has raised funds for 100 boxes each year, which it distributes to police departments that apply online. Cichon, the executive director, said the group has donated 400 boxes so far.

Cichon said there are two requirements to apply for a free drop off box: The location must be accessible to the public and it must already have means of disposing the drugs. Police departments, which routinely dispose of drugs they confiscate, easily meet those requirements.

Livingston, N.J., resident Grace Russo drops off medication at a collection box at the Livingston Police Department, installed at the end of June.(Photo: Livingston, N.J. Police Department)

Departments that have received drop off boxes in the last month:

• Ames, Iowa, Police Department: Ames received a box through the Rx Drug Drop Box grant two weeks ago and has already received 30 pounds of unused prescriptions, Huff said.

• Mason City, Iowa, Police Department: Captain Mike McKelvey said his department paid for a drop box out of its own budget. "We have a lot of nursing homes and elderly people where someone dies and people are asking us, 'What should we do with all this medication,' " McKelvey said. "Now we can direct them up here."

• Ontario County, N.Y., Sheriff's Office: Ontario received two drop off boxes through the nonprofit Partnership for Ontario. Sheriff Philip Povero said said so far about 100 pounds of drugs have been collected.

• Livingston, N.J., Police Department: Livingston installed a drop off box on June 30 and it was at full capacity by July 8. The department participated in national take-back days and had received more than 1,400 pounds of medication from local residents. Officer Gary Mankowitz said the department saw a need for a permanent collection box. "We have residents that could not come to Operation Take Back due to it being held on their Sabbath and also residents who would collect their drugs and then forget to bring them on the day of the event. Now they can drop them off whenever they would like," Mankowitz said in an email. "The program allows residents to deposit any type of drug with no questions asked."